Scientist Despina Fragouli and her colleagues at the Italian Institute of Technology found that mixing spent coffee grounds with a silicone product created a rubbery foam that is capable of separating out lead and mercury from water, according to a study published in the journal ACS Sustainable Chemistry & Engineering.

Other studies have shown that coffee in powder form can be used to extract metals from water, but often require the use of synthetic materials to do so.

“The proposed method is cheaper and more sustainable compared to other systems where synthetic materials are used,” Fragouli told Takepart.

Fragouli’s team was able to turn espresso coffee grounds into a powder, mixing it with silicone and sugar, and then baking it to create brown foam blocks that act as water filters.

The study reported that in still water, the foam removed 99 percent of lead and mercury traces. When the water flowed through the foam, it removed 67 percent of lead.

Fragouli added that the findings were surprising, as the foam blocks tested were natural products made up of 60 to 70 percent recycled coffee grounds, which are biodegradable.

“The efficiency of the coffee was preserved,” Fragouli said. “In this way, the porous composites can be safely and easily utilized and disposed of, making possible large-scale utilization.”

Fragouli added that she sees the foam blocks “being installed at industrial water sites and urban wastewater processing plants.”

“We are investigating if we can arrive to the acceptable limits for lead and mercury for drinkable water,” Fragouli said. “In order to arrive to a commercial product, we need to make further studies based on the exact application on which this material can be used.”